1. Field of the Invention
The present invention relates to a heat treatment apparatus and a method of controlling the same.
2. Description of the Related Art
In general, a vertical type heat treatment apparatus and a horizontal type heat treatment apparatus are known as apparatuses for performing a heat treatment, such as a film formation process, an oxidation process, and a diffusion process, on a semiconductor wafer. Among the apparatuses, the vertical type heat treatment apparatus is used mainly because the vertical type heat treatment apparatus generates less engulfment of air (for example, Patent Reference 1).
In these heat treatment apparatuses, in general, when a setting temperature or a ramping rate is changed, a ramping beginning temperature starts at a previous target temperature.
In a conventional heat treatment apparatus, when an actual temperature temporarily falls due to an external disturbance that occurs, for example, when a wafer boat is carried into the heat treatment apparatus, a large difference occurs between a target temperature and the actual temperature, and thus an output of the heat treatment apparatus increases. Thus, the actual temperature is overshot, and accordingly, it takes a long time to return an internal temperature of the heat treatment apparatus and a temperature of a semiconductor wafer to target temperatures.